1. Field
The disclosure relates to an apparatus to achieve with one processing line a very high uniform feeding capacity of long wood to a chipper. The wood processing apparatus described herein is especially meant for feeding debarked wood to a chipper, delivered as transportation bundles for chipping. Especially considered is the handling of transportation bundles of wood debarked in the forest, to be chipped for the pulp production, so that the wood can be transported to the chipper as an even flow. The wood to be processed has typically a length from 4 to 8 meters.
2. Description of Related Art
The traditional technique comprises a receiving table of log bundles and an unscrambling conveyor by means of which the log bundle placed on the receiving table is broken (discharged) to smaller lots. These smaller lots are fed forward one after another, substantially as a uniform log flow. The logs to be processed have been debarked in advance, especially in connection with the felling, as so called forest debarking. The debarking is not thorough, so that bark, including a share of the loosened bark, is unavoidably carried with the logs, the amount thereof being for example 3% of the wood quantity. The loose bark causes clogging problems on the receiving table and also on the unscrambling conveyor, and should be removed from the log bundles prior to feeding the logs to the chipper. The bark still present on the logs is preferably also removed before the chipper. The conventional apparatus combination including a receiving table and an unscrambling conveyor does not, however, provide any effective tools to remove the bark from the logs. Another problem with the apparatus is in reaching an adequate capacity with short or twisted logs or with logs having a small diameter.
In other techniques, long logs having a length of a whole trunk are transported from the forest unbarked, as truckload bundles, to a debarking drum. Thereby a common problem is that the log bundles are not totally broken in the drum, and an even feed to the chipper is arranged by adjusting the log flow coming from the drum by means of a grab bucket crane moving the logs as smaller batches. However, this technique does not guarantee a sufficient capacity for the system.
Also, logs debarked in the forest could be transported as truckload bundles for chipping. A device, a so-called tumbling drum is used for breaking of the bundles into an even log flow. The tumbling drum in question has a basic implementation corresponding to a debarking drum, in other words, it is substantially a horizontal cylinder, open at its both ends, rotatable about its longitudinal axis, but there are, however, certain differences with respect to the debarking drum.
The tumbling drum must be relatively short, because it is not meant for efficient debarking of the logs. A long tumbling length would increase breaking of the logs and cause wood losses. A typical design is about 1.5 to 3 times the average length of the logs to be processed, preferably about twice the average length of the logs. The diameter of the drum is chosen according to the required capacity, usually ranging from 3 to 6 m. The shell of the drum is usually solid. If necessary, there can be also openings n the shell for eventual discharging of rock material and/or loose bark. The drum is arranged inclining in the flow direction, having an angle of inclination in the flow direction of about 1:30 to 1:100. A suitable receiving and feeding apparatus precedes the drum. A suitable conveyor apparatus is arranged after the drum for feeding the log flow discharged from the transport bundle to be chipped. The conveyor apparatus can be for example a roller conveyor, whereby there is arranged the possibility for the loose bark and the other loose material to drop off from the log flow.
One problem discovered in the devices comprising a tumbling drum is the incomplete breaking of the log bundles. Increasing of the length of the drum is not a recommendable solution to the discovered problem, due to the increasing wood damages mentioned above.